Over 700,000 vertebral fractures occur each year in the United States. Eighty-five percent of these vertebral fractures are associated with osteoporosis. Osteoporosis causes bone to lose density and strength resulting in porous, weak bones especially susceptible to fracture.
Vertebroplasty is a non-surgical procedure for combating the effects of osteoporosis and the like, in which a vertebral body is structurally reinforced using a special cement-like substance, or bone cement. A typical bone cement for use in vertebroplasty is called “polymethylmethacrylate acrylic cement” (PMMA). Vertebroplasty has been used in the treatment of vertebral lesions (hemangoma), spreadable tumors of the spine (e.g. cancer), and osteoporotic vertebral fracture.
When performing vertebroplasty, the clinician uses fluoroscopy for needle placement and for monitoring the injection of bone cement within the vertebral body. Using a simple syringe, the clinician is exposed to excessive x-ray radiation within a fluoro field produced by a fluoroscope. It is well known that excessive exposure to x-ray radiation is dangerous and even cancer-causing. Thus, in order to reduce such exposure, the clinician should perform this procedure outside the range of the fluoro field.
Known techniques for keeping the clinician outside of the fluoro field typically involve the use of a long extension tube, whereby one end of the tube extends from an injection pump and the other end is coupled to a hollow bone needle. The extension tube is used as a conduit for delivering the bone cement from the pump to the bone needle for injection into the vertebral body. The additional length of the extension tube allows a clinician to perform the vertebroplasty at a distance outside the fluoro field.
A disadvantage of such injection devices is that the extension tube produces a pressure drop, making it more difficult to deliver the bone cement through the tube. Mechanisms can be implemented to increase the pressure for pushing the cement through the tube. However, such mechanisms typically reduce the natural feedback or “feel” of the injection device, resulting in a number of pressure concerns. For example, the lack of natural feedback can cause the clinician to inadvertently leak bone cement into the surrounding tissue or the spinal cord itself, resulting in a number of serious health risks. Furthermore, the additional length of the tube makes such injection devices susceptible to premature curing or hardening, resulting in the tube becoming clogged.